1. Field of the Invention
The present invention relates to a viscous coupling, and more particularly to a viscous coupling for connecting a vehicular drive shaft and a differential to each other and transmitting torque between a plurality of plates by utilizing shearing forces of a viscous fluid filled in the casing of the viscous coupling.
2. Description of the Relevant Art
One conventional viscous coupling has an enclosure comprising inner and outer cylindrical walls disposed concentrically with each other and rotatable relatively to each other, and end walls closing the opposite ends of the inner and outer cylindrical walls, as disclosed in U.S. Pat. No. 4,022,084, for example. The inner and outer cylindrical walls are drivingly coupled to respective two rotatable members of the differential. The enclosure is filled with a viscous fluid, and houses two sets of annular inner and outer interleaved plates alternately arranged at certain spaced intervals. The annular inner and outer plates are rotatable about a common axis, and are also movable axially to transmit torque therebetween through the utilization of shearing forces of the viscous fluid.
Each of the inner and outer plates has a plurality of holes defined therein for providing fluid communication between the spaces on the opposite sides of the plate. When the viscous fluid is introduced into the enclosure through an inlet in one end wall, the viscous fluid flows toward the other end wall through the holes in the inner and outer plates, but the viscous fluid flow has no directivity. The amount of the viscous fluid which flows through the holes in the plates is small, and most of the viscous fluid spreads radially outwardly from the inlet in the end wall and flows through a labyrinthine gap formed between the plates. It takes some time to supply the viscous fluid uniformly between the plates.